1. Field of the Invention
The present invention relates to a piezoelectric resonator element, a piezoelectric device, a method of manufacturing them, a cellular phone, and electronic equipment that utilize a piezoelectric device.
2. Related Art
In small information equipment such as a hard disc drive (HDD), a mobile computer, or an integrated circuit (IC) card, and mobile communication equipment such as a cellular phone, a car-phone, or a paging system, a piezoelectric device such as a crystal resonator and a crystal oscillator that contains a piezoelectric resonator element in a package has been widely used.
A piezoelectric resonator element contained in a conventional piezoelectric device has a structure including a base portion and a pair of resonating arm portions formed in a manner of protruding from the base portion (Refer to Japanese Unexamined Patent Publication No. 2002-261575 (FIG. 1, Page 5 and 7)).
Groove parts are formed on both of the front and back surfaces of resonating arm parts of the conventional piezoelectric resonator element, while notch parts are formed in the base portion.
However, in a tuning fork type resonator element with so-called grooves, which is a conventional piezoelectric resonator element, a temperature characteristic (frequency) that is the relationship between temperature changes and frequency tolerance changes shows a quadratic curve. Therefore, there is a problem that the changes of frequency tolerance due to temperature changes become large.
The present invention is devised in order to solve the above problem, and is intended to provide a piezoelectric resonator element, a piezoelectric device in which the changes of frequency tolerance in response to temperature changes is reduced so as to obtain an excellent temperature characteristic, a method of manufacturing them, a cellular phone device utilizing a piezoelectric device, and electronic equipment utilizing a piezoelectric device.